Purpose: Dendritic cells (DCs) are efficient and effective antigen-presenting cells that play a major role in initiating the primary immune response. They are the most potent stimulators of T-cell activation and would thus be expected to be of great importance in the antitumoral immune response. Although DC phenotype and function have been described under in vitro conditions, their in vivo characteristics are less well detailed. Human renal cell carcinoma (RCC) is an excellent model to explore tumor infiltrating dendritic cells (TiDCs) because of rare clinical spontaneous regressions and the association of high numbers of tumor infiltrating lymphocytes (TiLs), suggesting a strong immune response.
Materials and methods: We determined the in situ phenotype of mature CD83+ TiDCs using monoclonal antibodies to known activation molecules (CD86 [B7.2], CD80 [B7.1], CD40, CD54, CD1a and HLA-DR). Seventeen primary RCCs, representing four distinct histologies, were evaluated using double-staining immunohistochemical techniques and light microscopy.
Results: CD83+ TiDCs were found in all tumors. Expression of CD40 correlated with expression of CD1a on CD83+ TiDCs. Expression of CD54 (ICAM-1) correlated with a lower expression of CD86 (B7.2) as well as a decrease in CD3+ and CD8+ TiLs.
Conclusions: These data suggest a de novo lipid or sugar-based immunogenic antigen presentation by TiDCs. Also, the data support an impaired antigen-presenting capability for CD54+ TiDCs based on the decreased coexpression of CD86 (B7.2) and the decrease of associated CD8+ TiLs.